HP XP Array Manager Software - Manual (Page 31)

Figure 12 Setting upper limits
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6. Check the result of applying upper-limit values. After applying upper-limit values, you must
measure traffic at ports. View traffic statistics for the prioritized WWN to check whether the host
performance is improved to a desirable level.
In network B, the desirable I/O rate for the prioritized WWN is 400 IO/s. If the I/O rate reaches
400 IO/s, production server performance has reached to a desirable level. If production server
performance is not improved to a desirable level, you can change the upper-limit to a smaller
value and then apply the new upper-limit to the storage system. In network B, if the upper-limit is
set to 720 IO/s but the I/O rate for wwn01 is still below 400 IO/s, the administrator needs to
change the upper-limit until the I/O rate reaches 400 IO/s.
If an upper-limit of the non-prioritized WWN is set to zero or nearly zero, I/O performance might
be lowered. If I/O performance is lowered, the host cannot be connected to the storage system
in some cases.
7. If necessary, apply a threshold. To use threshold control, set a threshold in the WWN tab in the
Performance Control window.
In the WWN tab, you can specify only one threshold for the entire storage system, regardless of
the number of prioritized WWNs. For example, if there are three prioritized WWNs in the network
and the threshold is 100 IO/s, the upper-limit on the non-prioritized WWNs is disabled when
the sum of the I/O rates for all prioritized WWNs goes below 100 IO/s.
For details on how to set a threshold, see “
Setting a Threshold in the WWN Tab ” on page 42.
CAUTION:
If you enter zero (0) in a cell to disable the upper-limit, the cell displays a hyphen (-), and the threshold
for the prioritized port becomes ineffective. If the thresholds of all the prioritized ports are ineffective,
threshold control will not be performed but upper-limit control will be performed.
XP24000/XP20000 Performance Control User Guide 31